Ambient cure solvent-based coatings for writable-erasable surfaces

ABSTRACT

Solvent-based coatings having writable-erasable surfaces are provided. The coatings have many desirable attributes. For example, the coatings cure rapidly under ambient conditions, have low VOC emissions upon curing, and have reduced tendency to form ghost images, even after prolonged normal use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 61/082,029, filed on Jul. 18, 2008, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates to solvent-based coatings for writable-erasablesurfaces, products that include such coatings, and to the methods ofmaking and using the same.

BACKGROUND

Classroom education has traditionally relied upon a “blackboard” andchalk as an instruction medium. This technique can be messy, dusty, andmany blackboards cannot be used with all chalk types and colors. Thedust generated can lead to many respiratory afflictions. Overheadprojectors, laptop computers, and dry erase boards (often referred tocommonly as “whiteboards”) are alternatives to traditional blackboards.

Dry erase boards typically include a substrate, such as paper or board,and a coating, such as a lacquer coating, extending upon the substrate.The coating provides a writing surface that can be marked using dryerase marking pens. Dry erase marking pens, which are typically felt tipmarking instruments, contain inks that not only can mark such surfaces,but also can be erased with minimal effort using, e.g., a dry eraser,cloth, or paper tissue.

The erasability of dry erase inks from the writing surfaces of dry eraseboards can deteriorate over time, resulting in the formation ofnon-removable “ghost images.” In addition, such surfaces can beincompatible with some dry erase markers, and can be permanently markedif inadvertently written on with a permanent marker.

SUMMARY

This disclosure relates to coatings having writable-erasable surfaces,products that include such coatings (e.g., whiteboards), and to methodsof making and using the same. Generally, the coatings having thewritable-erasable surfaces are produced from one or more precursormaterials in a solvent-based carrier; the coatings cure under ambientconditions. When the writable-erasable surface is marked with a markingmaterial, the marking material can be erased to be effectively invisible(e.g., substantially invisible) with little or no ghosting, even afterprolonged and repeated use. The one or more materials that form thecoatings emit minimal volatile organic compounds (VOCs) after curing onthe substrate. The resulting coatings have many desirable attributes,including one or more of the following: low porosity, low surfaceroughness, high elongation at break, high Taber abrasion resistance, andhigh Sward hardness. Generally, while not intending to be bound by anytheory, it is believed that the low porosity of the coatings makes thecoatings substantially impervious to the marking materials, while thelow surface roughness prevents the marking materials from becomingentrapped on the surface beyond effective reach of an eraser.

In one aspect of the disclosure, a writable-erasable product includes acured coating (such as a cross-linked coating) extending upon asubstrate and having a writable-erasable surface. The coating can becured under ambient conditions, and can be formed from one or morematerials each independently including one or more substances includingone or more isocyanate groups, or one or more substances including oneor more hydroxyl groups. At least one of one or more materials can be ina solvent-based carrier. After the writable-erasable surface is markedwith a marking material including a colorant and a solvent, the markingmaterial can be erased from the writable-erasable surface to beeffectively invisible (e.g., substantially invisible).

In another aspect, the disclosure describes a writable-erasable productincluding a cured coating extending upon a substrate and having awritable-erasable surface. The coating can be cured under ambientconditions, and can be formed from one or more materials including oneor more of hexamethylene diisocyanate, its oligomers or homopolymers;one or more materials including one or more of an acrylic polyol; andone or more of an accelerator. At least one of one or more materials canbe in a solvent-based carrier. After the writable-erasable surface ismarked with a marking material including a colorant and a solvent, themarking material can be erased from the writable-erasable surface to beeffectively invisible (e.g., substantially invisible).

In another aspect, the disclosure describes a method of making awritable-erasable product, the method includes applying a coating to asubstrate, and curing the coating (e.g., under ambient conditions) toprovide a cured coating defining a writable-erasable surface. Thecoating can be formed from one or more materials each independentlyincluding one or more substances including isocyanate groups, or one ormore substances including hydroxyl groups. At least one of one or morematerials can be in a solvent-based carrier. After the writable-erasablesurface is marked with a marking material including a colorant and asolvent, the marking material can be erased from the writable-erasablesurface to be effectively invisible (e.g., substantially invisible).

In another aspect, the disclosure describes a method of changeablypresenting information including marking the writable-erasable surface,described herein, with a first information using a marking materialincluding a colorant and a solvent. The first information can be erased(e.g., by applying an eraser to the writable-erasable surface) from thewritable-erasable surface to be effectively (e.g., substantially)invisible. This is followed by marking the writable-erasable surfacewith a second information and again erasing the marking of the secondinformation from the writable-erasable surface to be effectively (e.g.,substantially) invisible.

In some implementations, the marking and erasing of information can beperformed repeatedly.

In another aspect, the disclosure describes a composition including analiphatic diisocyanate or their homopolymers and oligomers, an acrylicpolyol, an organic solvent, and optionally an accelerator and/or an acidpromoter.

In some implementations, the composition can include titanium dioxide, asurface additive, a wetting agent, a defoaming agent, a pigment, or acolorant.

In another aspect, the disclosure describes a writable-erasable productincluding a cured coating extending upon a substrate and having awritable-erasable surface. The coating can cure under ambient conditionsand can be formed from one or more materials. At least one of one ormore materials can be in a solvent-based carrier. After thewritable-erasable surface is marked with a marking material including acolorant and a solvent, the marking material can be erased from thewritable-erasable surface to be effectively invisible (e.g.,substantially invisible).

In some implementations, the one or more materials can be an epoxyresin, an acrylic monomer, a vinyl monomer, or an alkyd resin other thanan urethane alkyd.

The one or more of the above aspects of the disclosure can include oneor more of the following implementations.

In some implementations, the cured coating and/or the writable-erasablesurface may have one or more of the following attributes. The coatingmay have a porosity of less than about 40 percent; a thickness of fromabout 0.001 inch to about 0.125 inch; a Taber abrasion value of fromabout 100 mg/thousand cycles to about 125 mg/thousand cycles; a Swardhardness of greater than about 10; an elongation at break of betweenabout 5 percent and about 400 percent; a sag resistance of between about4 mils and about 24 mils. The writable-erasable surface can be erased tobe substantially invisible after writing and erasing at the sameposition for more than about 100 cycles, or even more than about 5,000cycles. The writable-erasable surface can have an average surfaceroughness (R_(a)) of less than about 7,500 nm; a maximum surfaceroughness (R_(m)) of less than about 10,000 nm; a contact angle ofgreater than about 35 degrees; a contact angle of less than about 150degrees.

In some implementations, the one or more substances including one ormore isocyanate groups can be selected from hexamethylene diisocyanate(HDI), tetramethylene diisocyanate, octamethylene diisocyanate,decamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, toluenediisocyanate (TDI), diphenylmethane diisocyanate (MDI), m- andp-phenylene diisocyanates, bitolylene diisocyanate, cyclohexanediisocyanate (CHDI), bis-(isocyanatomethyl)cyclohexane (H6XDI),dicyclohexylmethane diisocyanate (H12MDI), dimer acid diisocyanate(DDI), trimethyl hexamethylene diisocyanate, lysine diisocyanate and itsmethyl ester, methyl cyclohexane diisocyanate, 1,5-napthalenediisocyanate, xylene diisocyanate, polyphenylene diisocyanates,isophorone diisocyanate (IPDI), hydrogenated methylene diphenylisocyanate (HMDI), tetramethyl xylene diisocyanate (TMXDI), or theiroligomers and homopolymers, and their mixtures.

In some implementations, the one or more materials including one or moreisocyanate groups includes aliphatic diisocyanates (e.g.,hexamethylene-1,6-diisocyanate, IPDI and the like) or their oligomersand homopolymers, and their mixtures.

In some implementations, the one or more materials including one or moreisocyanate groups includes a polymeric material (e.g., homopolymerhexamethylene-1,6-diisocyanate).

In some implementations, the one or more substances including one ormore hydroxyl groups includes an α,ω-diol.

In some implementations, the one or more substances including one ormore hydroxyl groups includes a polymeric material (e.g., an acrylicpolyol, or an acrylic based diol).

In some implementations, the one or more materials including one or morehydroxyl groups also includes a cross-linking agent.

In some implementations, the accelerator includes dibutyltin dilaurate.

In some implementations, the one or more materials forming the coatingfurther includes an acid promoter such as a carboxylic acid (e.g.,acetic acid, propionic acid, butanoic acid, phosphoric acid, citric acidand the like).

In some implementations, the solvent-based carrier can includehydrocarbons (such as saturated hydrocarbons and unsaturatedhydrocarbons), alcohols (such as alkoxy alcohols, ketonic alcohols),ketones, esters (such as acetates), mineral spirits, bio-based solventsor mixtures thereof. Examples of such solvents can include ethylbenzene, toluene, xylene, naphtha (petroleum), petroleum distillates,n-butyl acetate, methyl iso-amyl ketone, Stoddard solvent, t-butylacetate, acetone, isopropyl alcohol, 2-butoxyethanol, toluene, methanol,propanol, 2-butanol, iso-amyl alcohol, methyl amyl alcohol, pentane,heptane, odorless mineral spirits, methyl ethyl ketone, diacetonealcohol, methyl amyl ketone, ethyl amyl ketone, diisobutyl ketone,methyl heptyl ketone, ethyl acetate, isopropyl acetate, propyl acetate,isobutyl acetate, n-butyl acetate, glycol ether EM acetate, amylacetate, isobutyl isobutyrate, glycol ether EE acetate, glycol ether EBacetate, 2-ethylhexyl acetate, glycol ether DE acetate, glycol DBacetate, methyl isobutyl ketone, dipropylene glycol butoxy ether,vegetable oil, corn oil, sunflower oil or their mixtures.

In some implementations, the substrate can be selected from the groupconsisting of cellulosic material, glass, wall (such as plaster orpainted wall), fiber board (e.g., a whiteboard in which the curedcoating can be extending upon a fiber board), particle board (e.g., achalkboard or blackboard), gypsum board, wood, plastics (such as highdensity polyethylene (HDPE), low density polyethylene (LDPE), or aacrylonitrile, butadiene, styrene (ABS)-based material), densifiedceramics, stone (such as granite), and metal (such as aluminum orstainless steel).

In some implementations, the substrate can be selected from a flexiblefilm or a rigid structure.

In some implementations, the marking material includes a solventincluding water, alcohols (such as alkoxy alcohols, ketonic alcohols),ketones, esters (such as acetates), mineral spirits, bio-based solvents,or their mixtures.

In some implementations, the marking material can be erased from thewritable-erasable surface to be effectively invisible by wiping themarks with an eraser including a fibrous material (such as a papertowel, rag, or felt material).

In some implementations, the eraser is dry or includes water, alcohol(e.g., ethanol, n-propanol, isopropanol, n-butanol, isobutanol, benzylalcohol), alkoxy alcohol (e.g., 2-(n-propoxy)ethanol,2-(n-butoxy)ethanol, 3-(n-propoxy)ethanol), ketone (e.g., acetone,methyl ethyl ketone, methyl n-butyl ketone), ketonic alcohol (e.g.,diacetone alcohol), ester (e.g., methyl succinate, methyl benzoate,ethyl propanoate), acetate (e.g., methyl acetate, ethyl acetate, n-butylacetate, t-butyl acetate), mineral spirit, or mixtures thereof.

In some implementations, the writable-erasable product can take the formof a whiteboard, in which the cured coating extends upon a fiberboard;can form a part of a wall e.g., of a structure; or can form a pluralityof sheets, each sheet including a substrate (e.g., in the form of apaper) having the cured coating extending thereupon.

In some implementations, the coating can be prepared by combining theone or more materials including one or more isocyanate groups, and theone or more materials including one or more hydroxyl groups.

In some implementations, prior to combining, the one or more materialsincluding one or more isocyanate groups can be in a first container, andthe one or more materials including one or more hydroxyl groups can bein a second container.

In some implementations, the erasing is performed by applying an eraser(such as including a fibrous material) to the writable-erasable surface.

In some implementations, the eraser includes water, alcohols (such asalkoxy alcohols, ketonic alcohols), ketones, esters (such as acetates),mineral spirit, or their mixtures.

Implementations and/or aspects may include one or more of the followingadvantages. The coating surfaces are writable and erasable. The coatingscan provide writing surfaces that exhibit little or no image ghosting,even after prolonged normal use. The coatings can be simple to prepare,and can be applied to many different substrates, including both porous(e.g., paper) and non-porous substrates (e.g., densified ceramics). Thecoatings can be applied to various substrates including, but not limitedto, chalkboards (e.g., blackboards), whiteboards, drywalls, gypsumboards, plaster and painted walls. The solvent based coatings can beapplied on the substrate on-site rather than being manufactured in afactory. For many substrates, a single coating can provide an adequatewritable-erasable surface. The coatings can exhibit good adhesivestrength to many substrates. Coating components (prior to mixing) canhave an extended shelf-life, e.g., up to about three years or even up tosix years. The coatings can be readily resurfaced. The coatings can curerapidly, e.g., in less than 4 hours, under ambient conditions. Thecoatings can resist yellowing, as determined by ASTM method G-154, foran extended period of time (e.g., up to 2000 hours or even up to 5000hours). The coatings do not require UV light or high-energy radiation,such as a beam of electrons, for curing. Nevertheless, in someimplementations, light, e.g., UV light, or heat can be utilized toenhance the curing rate. The coatings can have a reduced tendency torun, even when applied upon a vertical substrate. Surface gloss of thecoatings can be readily adjusted. The writing surface of the coating canbe projectable. The coatings can be hard. The coatings can besubstantially impervious to organic solvents and/or inks. The coatingscan have a low porosity. Surfaces of the coatings can have a lowroughness. The coatings can be impact resistant. The coatings can bemade scratch and abrasion resistant. The coatings can be relatively lowcost. The coatings can have a high chemical resistance.

“Curing” as used herein, refers to a process of setting (e.g., byevaporation (drying) or cross-linking) a material to form a coating on asubstrate. Curing can be performed by exposure to ambient conditions,radiation; or cross-linking (e.g., oxidative cross-linking).

“Solvent-based” as used herein refers to a mixture predominantlycontaining organic solvents. Such organic solvents may be used either intheir anhydrous or wet form unless specified otherwise.

“Ambient conditions” as used herein refers to nominal, earth-boundconditions as they exist at sea level at a temperature of about 45-130°F.

“Effectively invisible” as used herein refers to a color differenceDelta E (ΔE) of less than 20 as calculated according to the ASTM TestMethod D2244 before and after a mark is erased by an eraser.

“Substantially invisible” as used herein refers to a color differenceDelta E (ΔE) of less than 10 as calculated according to the ASTM TestMethod D2244 before and after a mark is erased by an eraser.

“Alkyl” as used herein, refers to a saturated or unsaturated hydrocarboncontaining 1-20 carbon atoms including both acyclic and cyclicstructures (such as methyl, ethyl, propyl, isopropyl, butyl, iso-butyl,sec-butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, propenyl, butenyl, cyclohexenyl and the like). A linkingdivalent alkyl group is referred to as an “alkylene” (such as ethylene,propylene and the like).

As used herein, “aryl” refers to monocyclic or polycyclic (e.g., having2, 3 or 4 fused rings) aromatic hydrocarbons such as, phenyl, naphthyl,anthracenyl, phenanthrenyl, indanyl, indenyl, and the like. In someembodiments, aryl groups have from 6 to 20 carbon atoms, from 6 to 15carbon atoms, or from 6 to 10 carbon atoms.

As used herein, “heteroaryl” refers to an aromatic heterocycle having atleast one heteroatom ring atom such as sulfur, oxygen, or nitrogen.Heteroaryl groups include monocyclic and polycyclic (e.g., having 2, 3,or 4 fused rings) systems. Examples of heteroaryl groups include withoutlimitation, pyridyl, furyl, quinolyl, indolyl, oxazolyl, triazolyl,tetrazolyl, and the like. In some embodiments, the heteroaryl group hasfrom 1 to 20 carbon atoms (e.g., from 3 to 20 carbon atoms). In someembodiments, the heteroaryl group has 1 to 4 heteroatoms (e.g., 1 to 3,or 1 to 2 heteroatoms).

As used herein, “aralkyl” refers to alkyl substituted by aryl. Anexample aralkyl group is benzyl.

As used herein, “alkoxy” refers to an —O-alkyl group. Example alkoxygroups include methoxy, ethoxy, propoxy (e.g., n-propoxy andisopropoxy), t-butoxy, and the like.

As used herein, “oxyalkylene” refers to an —O-alkylene group.

As used herein, “alkoxylate” refers to an alkyl-C(O)O. Examplealkoxylates include acetate, stearate and the like.

As used herein, “halo” includes fluoro, chloro, bromo, and iodo.

A “polyol” as used herein is a moiety that includes at least twohydroxyl (—OH) groups. The hydroxyl groups can be terminal and/ornon-terminal. The hydroxyl groups can be primary hydroxyl groups.

A “polyurethane” as used herein is a polymeric or oligomeric materialthat includes a urethane linkage, [NHC(═O)O], in its backbone.

All publications, patent applications, patents, and other referencesmentioned herein are hereby incorporated by reference herein in theirentirety.

It is to be further appreciated that certain features of the invention,which are, for clarity, described in the context of separateembodiments, can also be provided in combination in a single embodiment.Conversely, various features of the invention which are, for brevity,described in the context of a single embodiment, can also be providedseparately or in any suitable subcombination.

The details of one or more implementations of the disclosure are setforth in the accompanying drawings, and in the description below. Otherfeatures, and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of a writable-erasable product.

FIG. 1A is a cross-sectional view of the writable-erasable product ofFIG. 1, along 1A-1A.

FIG. 2 is a cross-sectional view of a droplet of water on a coating andillustrates a method for determining contact angle.

FIG. 3 is a perspective view of a coated roll of paper.

FIG. 4 is a perspective view of a tablet of coated papers formed fromthe roll of FIG. 3.

Like reference symbols in various drawings indicate like elements.

DETAILED DESCRIPTION

Writable-Erasable Product

Referring to FIGS. 1 and 1A, a writable-erasable product 10 includes asubstrate 12 and a coating 14 (e.g., a cured coating) extending upon thesubstrate 12. The cured coating 14 has a writable-erasable surface 16.When the writable-erasable surface 16 is marked with a marking material,the marking material can be erased from the writable-erasable surface tobe effectively (e.g., substantially) invisible, resulting in little orno ghosting, even after prolonged normal use, for example, after about10 cycles (e.g., after about 50 cycles, after about 100 cycles, afterabout 500 cycles, after about 1,000 cycles, after about 2,000 cycles,after about 3,000 cycles, after about 4,000 cycles, after about 5,000cycles, after about 6,000 cycles, after about 7,000 cycles, after about8,000 cycles, or after about 9,000 cycles) of writing and erasing at thesame position. The visibility, or the lack thereof, of the erasing canbe determined by measuring the color change (Delta E, ΔE) on thewritable-erasable surface using a spectrophotometer (such as the SP-62portable spectrophotometer available from X-Rite), after marking on thesurface and erasing the marking. The color change is a composite ofthree variables, lightness (L*), red/green value (a*), and yellow/bluevalue (b*). The erasability characteristics of the writable erasablesurface 16 can be defined in terms of the ΔE value. In someimplementations, the ΔE for the writable-erasable surface 16 after 5,000cycles (or even after 10,000 cycles) can be less than about 50, e.g.,less than about 40, less than about 30, less than about 20, less thanabout 10, less than about 9, less than about 8, less than about 7, lessthan about 6, less than about 5, less than about 4, less than about 3,less than about 2, or less than about 1.

In some implementations, the ΔE for the writable-erasable surface 16after 5,000 cycles (or even after 10,000 cycles) can be from about 0.1to about 10.0, e.g., from about 0.1 to about 0.5, from about 0.5 toabout 1.0, from about 1.0 to about 1.5, from about 1.5 to about 2.0,from about 2.0 to about 2.5, from about 2.5 to about 3.0, from about 3.0to about 3.5, from about 3.5 to about 4.0, from about 4.0 to about 4.5,from about 4.5 to about 5.0, from about 5.0 to about 5.5, from about 5.5to about 6.0, from about 6.0 to about 6.5, from about 6.5 to about 7.0,from about 7.0 to about 7.5, from about 7.5 to about 8.0, from about 8.0to about 8.5, from about 8.5 to about 9.0, from about 9.0 to about 9.5,or from about 9.5 to about 10.0.

It is to be appreciated that the erasability characteristic may also beevaluated based on the differences in L* (ΔL*), without attribution tocolor differences. This evaluation can also be combined with theprogressive abrasion of the coating on an abrader, such as the Taberabrader 4360. The abrasion of the coating can be performed similar tothe ASTM Method D4060. In this instance, the erasability characteristicas a function of the abrasion can be determined by abrading thewritable-erasable surface 16 for a certain number of cycles and thenmeasuring the change in lightness (ΔL*) value after marking on thesurface followed by erasing the marking. Typically, a substrate with acured coating can be loaded on an abrader and abrasive wheels can berotated on the writable-erasable surface 16 for a certain number ofcycles (e.g., 50 cycles, 100 cycles, 150 cycles, 200 cycles, 500 cycles,or 1,000 cycles). After each abrasive cycle, a spectrophotometer (suchas the SP-62 portable spectrophotometer available from X-Rite) can beused to measure the L* of the abraded area (L*_(A)) and thewritable-erasable surface 16 can be marked with a marking material (suchas an Expo 1 or Expo 2, Blue or Black marker) and erased (such as withan Expo felt dry Eraser). A spectrophotometer (such as the SP-62portable spectrophotometer available from X-Rite) can be used to measurethe L* value of the erased area (L*_(B)). The ΔL* can be determined fromthe difference of L^(*) _(A) and L^(*) _(B) values. In someimplementations, the ΔL* value for the writable-erasable surface 16after 1,000 cycles can be at least about 20, e.g., at least about 30, atleast about 40, at least about 50, at least about 60, at least about 65,at least about 70, at least about 75, at least about 80, at least about85, at least about 90, or at least about 99. In some otherimplementations, the ΔL* value for the writable-erasable surface 16after 1,000 cycles can be at least about 65, e.g., at least about 67, atleast about 69, at least about 71, at least about 73, at least about 75,at least about 77, at least about 79, at least about 81, at least about83, at least about 85, at least about 87, at least about 89, or at leastabout 91. In yet other implementations, the ΔL* value for thewritable-erasable surface 16 after 1,000 cycles can be from about 65 toabout 70, from about 70 to about 75, from about 75 to about 80, fromabout 80 to about 85, from about 85 to about 90, from about 90 to about95, or from about 95 to about 99.

The marking material can include a colorant (e.g., a pigment) and asolvent such as water, alcohol (such as alkoxy alcohol, ketonicalcohol), ketone, ester (such as acetate), mineral spirit, bio-basedsolvents (e.g., vegetable oil, corn oil, sunflower oil), or mixturesthereof. Bio-based solvents are alternatives to conventional organicsolvents and can be obtained from agricultural products. Such solventscan provide lower volatile organic compounds in coatings and decreasedenvironmental impact. The marking material can be selected from any ofthe industry standard dry-erase markers.

The materials that form the coating 14 can be applied to many differenttypes of substrates, including porous (e.g., paper) and non-poroussubstrates (e.g., densified ceramics). The substrate 12 can be aflexible film or a rigid movable or immovable structure. Examples of thesubstrate include, but not limited to, a polymeric material (such as apolyester or a polyamide), a cellulosic material (such as paper), glass,wood, plastics (such as HDPE, LDPE, or an ABS-based material), a wall(such as a plaster or painted wall), a fiber board (such as a whiteboardin which the cured coating extends upon a fiber board), a particleboard, (such as a chalkboard or blackboard), a gypsum board, densifiedceramics, stone (such as granite), and a metal (such as aluminum orstainless steel). The substrate could be a newly built structure or evenan old and worn out chalkboard, blackboard, or whiteboard. In someinstances, the surface of the substrate can be cleaned by sanding thesurface and priming the surface prior to application of the coating. Insome instances, the surface can also be cleaned with a cleaning agent(e.g., acetone or a mild acid) in order to provide better adhesion ofthe coating to the surface.

The materials that form the coating 14, prior to the application onsubstrates, can have a pot life which is the period during which thematerials must be applied on the substrate. In some implementations, thematerials can have a pot life of from about 10 minutes to about 16hours, for example, from about 30 minutes to about 12 hours, from about60 minutes to about 8 hours, from about 1 hour to about 4 hours, or fromabout 1 hour to about 2 hours. In other implementations, the materialscan have a pot life of greater than about 6 months, for example, about12 months, about 18 months, about 24 months, about 30 months, or about36 months.

The materials that form the coating 14, upon application to thesubstrates, typically cure under ambient conditions. While not intendingto be bound by any theory, it is believed that cross-linking betweenpolymeric chains can influence certain unique properties of coatings. Insome optional implementations, the curing can be facilitated byultra-violet (UV) light, thermal means, initiators, or electron-beam.The coating 14 can cure under ambient conditions in from about 4 hoursto about a week, e.g., from about 4 hours to about 24 hours, from about8 hours to about 20 hours, from about 12 hours to about 16 hours, fromabout 1 day to about 7 days, from about 2 days to about 6 days, or fromabout 3 days to about 5 days. The cured coating 14 can be generallystable and also emit little or no VOCs after curing. Curing underambient conditions can reduce environmental impact and can make thematerials safer to use.

The porosity of a coating can determine the amount of marking materialthat can be trapped in the coating. While not intending to be bound byany theory, it is believed that lower porosity of coatings can lead tobetter writable-erasable surfaces. In some implementations, the coating14 can have a porosity of between about 1 percent and about 40 percent,e.g., between about 2 percent and about 35 percent, between about 2.5percent and about 30 percent, or between about 3 percent and about 20percent. In other implementations, the coating 14 can have a porosity ofless than about 40 percent, e.g., less than about 35 percent, less thanabout 30 percent, less than about 25 percent, less than about 20percent, less than about 15 percent, less than about 10 percent, lessthan about 5 percent, or even less than about 2.5 percent.

In some implementations, the coating can have a porosity of betweenabout 2 percent and about 45 percent, e.g., between about 2.5 percentand about 35 percent or between about 3 percent and about 35 percent. Insome specific implementations, the coating can have a porosity of about3 percent, about 33 percent or about 34 percent.

The coating formulations can be prepared by standard techniques known toone skilled in the art. For example, during a grind stage,pre-determined amounts of the materials to be used in the formulationcan be mixed at required speeds in high shear dispersers until thematerials are homogeneously dispersed. The degree of dispersion of thematerials and pigments can be determined with a Hegman gauge. Theremaining materials, if any, can be introduced at a letdown stage toobtain the final formulation before being packaged. In two-componentcoating formulations, the two parts are mixed thoroughly and can beallowed to stand for a period of time before it can be applied on asubstrate.

The coating formulation can be applied on a substrate 12 in a singlecoat or multiple coats using a roller, a spray (such as an aerosolspray), a brush or using other types of applicators. In someimplementations, it can be painted using a foam roller in a single coat.In some implementations, the coating 14 can have a thickness, T (FIG.1A), e.g., between about 0.001 inch and about 0.125 inch, e.g., betweenabout 0.002 inch and about 0.1 inch, between about 0.004 inch and about0.08 inch, between about 0.006 inch and about 0.06 inch, between about0.008 inch and about 0.04 inch, or between about 0.01 inch and about0.02 inch). In other implementations, the coating 14 can have athickness of greater than about 0.005 inch, e.g., greater than about0.0075 inch or greater than about 0.010 inch. While not intending to bebound by any theory, it is believed that providing an uniform, adequatecoating thickness, T, reduces the likelihood of thin or uncoatedsubstrate portions where marking material might penetrate.

In some implementations, the coating 14 can have a Taber abrasion valueof less than about 150 mg/thousand cycles, e.g., less than about 100mg/thousand cycles, less than about 75 mg/thousand cycles, less thanabout 50 mg/thousand cycles, less than about 35 mg/thousand cycles, lessthan about 25 mg/thousand cycles, less than about 15 mg/thousand cycles,less than about 10 mg/thousand cycles, less than about 5 mg/thousandcycles, less than about 2.5 mg/thousand cycles, less than about 1mg/thousand cycles, or even less than about 0.5 mg/thousand cycles.Maintaining a low Taber abrasion value can provide long-lastingdurability to the coating, reducing the incidence of thin spots, whichcould allow penetration of marking material through the coating and intothe substrate.

In some implementations, the coating 14 can have a Sward hardness ofgreater than about 10, e.g., greater than about 15, greater than about25, greater than about 50, greater than about 75, greater than about100, greater than about 120, greater than about 150, or even greaterthan about 200. While not intending to be bound by theory, it isbelieved that maintaining a high Sward hardness provides long-lastingdurability and scratch resistance to the coating. Marking materialentrapped in scratches can be difficult to erase.

In some specific implementations, the coating 14 can have a Swardhardness of between about 10 and about 75, e.g., between about 15 andabout 70 or between about 15 and about 55. In some specificimplementations, the coating can have a Sward hardness of about 15,about 22 or about 25.

In some implementations, elongation at break for the coating materialcan be between about 5 percent and about 400 percent, e.g., betweenabout 25 percent and about 200 percent, or between about 50 percent andabout 150 percent. In other implementations, the elongation at break canbe greater than about 10 percent, e.g., greater than about 25 percent,greater than about 50 percent, or even greater than about 100 percent.While not intending to be bound by theory, it is believed thatmaintaining high elongation at break provides long-lasting durability tothe coating, and it allows the coating to be stressed without formingcracks. Cracks can trap marking materials, making erasure from surfacesdifficult and hence decreasing the longevity of the writable-erasableproducts.

In some implementations, the sag resistance for the coating material canbe at least about 3 mils, e.g., about 4 mils, about 5 mils, about 6mils, about 7 mils, about 8 mils, about 9 mils, about 10 mils, about 12mils, about 14 mils, about 16 mils, about 18 mils, about 20 mils, about22 mils, or about 24 mils. In other implementations, the coating 14 canhave a sag resistance of from about 4 mils to about 24 mils, e.g., fromabout 5 mils to about 20 mils, from about 6 mils to about 18 mils, fromabout 7 mils to about 16 mils, from about 8 mils to about 14 mils, fromabout 9 mils to about 12 mils, or from about 10 mils to about 12 mils.

In some implementations, the writable-erasable surface 16 can have anaverage surface roughness (R_(a)) of between about 0.5 nm and about7,500 nm, e.g., between about 1 nm and about 6,000 nm, between about 2nm and about 5,000 nm, between about 5 nm and about 2,500 nm, betweenabout 10 nm and about 1,500 nm, between about 20 nm and about 1,000 nmor between about 25 nm and about 750 nm. In other implementations, thewritable-erasable surface 16 can have an average surface roughness(R_(a)) of less than about 7,500 nm, e.g., less than about 5,000 nm,less than about 3,000 nm, less than about 2,000 nm, less than about1,000 nm, less than about 500 nm, less than about 250 nm, less thanabout 200 nm, less than about 100 nm, or even less than about 50 nm.

In some specific implementations, the writable-erasable surface 16 canhave an average surface roughness (R_(a)) of between about 75 nm andabout 1,000 nm, e.g., between about 100 nm and about 500 nm or betweenabout 150 nm and about 400 nm. In some specific implementations, thewritable-erasable surface 16 can have an average surface roughness(R_(a)) of about 150 nm, about 300 nm or about 1,000 nm.

In some implementations, the writable-erasable surface 16 can have amaximum surface roughness (R_(m)) of less than about 10,000 nm, e.g.,less than about 8,000 nm, less than about 6,500 nm, less than about5,000 nm, less than about 3,500 nm, less than about 2,000 nm, less thanabout 1,000 nm, or less even than about 500 nm.

In some implementations, the writable-erasable surface 16 can have aflat finish (gloss below 15, measured at 85 degrees), an eggshell finish(gloss between about 5 and about 20, measured at 60 degrees), a satinfinish (gloss between about 15 and about 35, measured at 60 degrees), asemi-gloss finish (gloss between about 30 and about 65, measured at 60degrees), or gloss finish (gloss greater than about 65, measured at 60degrees).

In some specific implementations, the writable-erasable surface 16 canhave a 60 degree gloss of between about 45 and about 90, e.g., betweenabout 50 and about 85. In other implementations, the writable-erasablesurface 16 can have a 20 degree gloss of between about 10 and about 50,e.g., between about 20 and about 45. In still other implementations, thewritable-erasable surface 16 can have a 85 degree gloss of between about45 and about 90, e.g., between about 75 and about 90. In other specificimplementations, the writable-erasable surface 16 can have a 20 degreegloss of about 12, about 23, or about 46; or a 60 degree gloss of about52, about 66, or about 85; or a 85 degree gloss of about 64, about 78,or about 88.

In some implementations, to improve the writability and erasability ofthe surface 16 of the coating 14, precursor materials can be chosen sothat the cured coating 14 has a surface that is relatively hydrophilicand not very hydrophobic. Referring to FIG. 2, hydrophobicity of thewritable-erasable surface 16 is related to its wettability by a liquid,e.g., a water-based marking material. It is often desirable to quantifythe hydrophobicity of the writable-erasable surface 16 by a contactangle. Generally, as described in ASTM D 5946-04, to measure contactangle, 0, for a liquid (such as water) on the writable-erasable surface16, an angle is measured between the writable-erasable surface 16 and atangent line 26 drawn to a droplet surface of the liquid at athree-phase point. Mathematically, θ is 2× arctan(A/r), where A is theheight of the droplet image, and r is half width at the base. In someimplementations, it can be desirable for the writable-erasable surface16 to have contact angle, θ, measured using deionized water, of lessthan about 150 degrees, e.g., less than about 125 degrees, less thanabout 100 degrees, less than about 75 degrees or even less than about 50degrees. In other implementations, it can be desirable for thewritable-erasable surface 16 to have contact angle θ above about 35degrees, e.g., above about 40 degrees, or above about 45 degrees.

In certain implementations, contact angle, θ, measured using deionizedwater, can be between about 30 degrees and about 90 degrees, e.g.,between about 45 degrees and about 80 degrees, or between about 39degrees and about 77 degrees. In some specific implementations, thecontact angle can be about 40 degrees, for example, about 50 degrees,about 60 degrees, about 73 degrees, or about 77 degrees.

In some implementations, the writable-erasable surface 16 can have asurface tension of between about 30 dynes/cm and about 60 dynes/cm,e.g., between about 40 dynes/cm and about 60 dynes/cm. In some specificimplementations, the writable-erasable surface 16 can have a surfacetension of about 25 dynes/cm, about 30 dynes/cm, about 42 dynes/cm,about 44 dynes/cm or about 56 dynes/cm.

In general, the coating 14 can be formed by applying (e.g., rolling,painting, or spraying) a solution of the material in a solvent-basedcarrier that can have a sufficient viscosity such that the appliedcoating 14 does not run soon after it is applied or during its curing.At the same time, the solution viscosity should be sufficient to permiteasy application. In some implementations, the applied solution can havea viscosity at 25° C. of between about 75 mPa·s and about 20,000 mPa·s,e.g., between about 200 mPa·s and about 15,000 mPa·s, between about1,000 mPa·s and about 10,000 mPa·s, or between about 750 mPa·s and about5,000 mPa·s.

Advantageously, when the writable-erasable surface 16 is marked with amarking material that includes a colorant and a solvent, the markingmaterial can be erased from the writable-erasable surface to beeffectively (e.g., substantially) invisible. The solvent includes one ormore of water, alcohols (such as alkoxy alcohols, ketonic alcohols),ketones, esters (such as acetates), mineral spirits, or bio-basedsolvents (e.g., vegetable oil, corn oil, or sunflower oil). Mixtures ofany of the noted solvents can also be used. For example, mixtures oftwo, three, four or more of the noted solvents may be used.

In some implementations, the marking material can be erased from thewritable-erasable surface 16 to be effectively (e.g., substantially)invisible by wiping the marks with an eraser that includes a fibrousmaterial. For example, the eraser can be in the form of a disposablewipe, a cloth, or a supported (e.g., wood, plastic) felt. The eraser canalso include a solvent such as water, alcohols (e.g., alkoxy alcohols,ketonic alcohols), ketones, esters, (e.g., acetates), or mineralspirits. Mixtures of any two or more of these solvents can also be used.

Examples of alcohols that can be used in the marking material or theeraser include ethanol, n-propanol, iso-propanol, n-butanol,iso-butanol, benzyl alcohol, 2-(n-propoxy)ethanol, 2-(n-butoxy)ethanoland 3-(n-propoxy)ethanol.

Examples of ketones that can be used in the marking material or theeraser include acetone, methyl ethyl ketone and methyl n-butyl ketone.

Examples of esters that can be used in the marking material or theeraser include methyl acetate, ethyl acetate, n-butyl acetate andt-butyl acetate.

For testing, the coating 14 can be made by casting a material on afluoropolymer substrate, and then curing the material so that it canhave a dry thickness of about 0.002 inch. The cured sample can then beremoved from the fluoropolymer substrate to provide the test specimen.Testing can be performed at 25° C. Elongation at break can be measuredusing ASTM method D-882; porosity can be measured using mercuryporosimetry (suitable instruments available from Micromeritics,Norcross, Ga., e.g., Micromeritics Autopore IV 9500); surface roughnesscan be measured using atomic force microscopy (AFM) in tapping modeusing ASME B46.1 (suitable instruments, e.g., WYKO NT8000, are availablefrom Park Scientific); Taber abrasion resistance can be measuredaccording to ASTM method D-4060 (wheel CS-17, 1 kg load) and Swardhardness can be measured according to ASTM method D-2134 (Sward HardnessRocker Model C). The amount of VOCs can be determined using the EPAMethod 24. Gloss can be measured using ASTM method D-523-89 (BYKTri-Gloss Meter Cat. No. 4525). Contact angle can be measured withdeionized water using the dynamic contact angle method (Angstroms ModelFTA 200) using ASTM method D-5946-04. Sag resistance can be measuredusing ASTM method D4400 which can be performed by obtaining a draw-downand measuring visually by comparison with standard ASTM pictures.Surface tension can be measured using AccuDyne Marking Pens. StormerViscosity can be measured on a Brookfield Viscometer by ASTM methodD-562 and reported in Kreb units (Ku).

Any writable-erasable product described herein can have any one or moreof any of the attributes described herein. For example, thewritable-erasable surface can have an average surface roughness (R_(a))of less than about 7,500 nm, a maximum surface roughness (R_(m)) of lessthan about 7,500 nm, a 60 degree gloss of less than about 50 and acontact angle of less than about 100 degrees.

Any coatings described herein can have any one or more of any of thefollowing attributes. For example, the coating can have a porosity ofless than about 45 percent, an elongation at break of between about 25percent and about 200 percent, and/or a Sward hardness of greater thanabout 3 and a Taber abrasion value of less than about 150 mg/thousandcycles.

Formulations

Solvent-based coatings utilize solvents to disperse or dissolve theresins and other ingredients to provide uniform dispersions orsolutions. The use of solvent-based systems can provide a durable, highquality finish in many applications. Solvent-based coatings also displayease of application and present less restrictions to achieving desiredproperties in a formulation due to the range of solvents that can bechosen during formulation. Further, solvent-based coatings can beapplied on a broader range of substrates.

The cured coating 14 having the writable-erasable surface 16 can beformed under ambient conditions from an uncured coating formulation. Thecoating formulations, in general, can include the materials describedbelow. The formulations can include either a one-component system or amulti-component system (e.g., a two-component system). A one-componentsystem, for example, consists of a coating formulation material packagedto be ready for use. A two-component system, for example, consists oftwo coating materials that are mixed, when desired, to obtain the finalcoating formulation prior to application on the substrate.

Polyurethanes

Polyurethanes can be obtained by the reaction of a diisocyanate orpolyisocyanate with a diol or a polyol. Polyurethanes exhibit a widerange of hardness and flexibility depending on various factors includingthe nature of the isocyanate-containing substance and/or thehydroxyl-containing substance as well as the nature of curing.Polyurethane coatings could either be formulated as one-component ortwo-component coatings. Reactive polyurethane coatings typically involveusing isocyanate and hydroxyl as the reactive groups during curing. See:The ICI Polyurethanes Book, George Woods. (John Wiley & Sons: New York,1987), and Organic Coatings-Properties, Selection and Use U.S.Department of commerce, National Bureau of Standards: Washington D.C.,Series 7; Feb. 1968, the complete disclosures of which are incorporatedby reference herein. Polyurethane coatings have also been categoricallyassigned several ASTM designations (Types I-VI).

For example, the coating 14 described in FIG. 1 can be formed from oneor more materials including one or more isocyanate (such asdiisocyanante) and one or more materials including one or more hydroxyl,at least one of these materials can be in a solvent-based carrier, e.g.,an organic solvent. In some implementations, the coating can be orincludes a reaction product of a first component that includes anisocyanate and a second component that includes a hydroxyl containingcompound (such as a polyol). Diisocyanates for use in polyurethaneapplications, in general, can be obtained by the reaction of amines withphosgene. Examples of organic diisocyanates include aliphatic,cycloaliphatic (alicyclic), and aromatic diisocyanates. e.g., methylenediisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate(HDI), octamethylene diisocyanate, decamethylene diisocyanate,2-methylpentane-1,5-diisocyanate, toluene diisocyanate (TDI),diphenylmethane diisocyanate (MDI), m- and p-phenylene diisocyanates,4-chloro-m-phenylene diisocyanate, bitolylene diisocyanate, cyclohexanediisocyanate (CHDI), bis-(isocyanatomethyl)cyclohexane (H6XDI),dicyclohexylmethane diisocyanate (H12MDI), dimer acid diisocyanate(DDI), trimethyl hexamethylene diisocyanate, lysine diisocyanate and itsmethyl ester, methyl cyclohexane diisocyanate, 1,5-napthalenediisocyanate, xylene diisocyanate, polyphenylene diisocyanates,isophorone diisocyanate (IPDI), hydrogenated methylene diphenylisocyanate (HMDI), tetramethyl xylene diisocyanate (TMXDI),4-t-butyl-m-phenylenediisocyanate, 4,4′-methylene bis(phenylisocyanate), tolylene diisocyanate, 4-methoxy-m-phenylene diisocyanate,biphenylene diisocyanate, cumene-2,4-diisocyanate,3,3′-dimethyl-4,4′-biphenylene diisocyanate, p,p′-diphenylenediisocyanate, or oligomers and homopolymers thereof, and mixturesthereof.

The monomeric diisocyanates may further be converted into oligomericprepolymers of higher molecular weight by treatment with diols ortriols. Such oligomeric prepolymers can also be used as a reactioncomponent in the production of the polyurethane coating. Diisocyanatesfor use in polyurethane applications can be available from variouscommercial vendors under different trade names. Examples of commercialdiisocyanates include, but are not limited to, diphenylmethanediisocyanate (MDI) containing ISONATE™, PAPI™, SPECTRIM™ (available fromDow chemical company); Desmodur® polyisocyanates and Bayhydur®(available from Bayer); Sovermol® (available from Cognis); Reafree® andChempol® (both available from Cook Composite Polymers).

In some implementations, the percentage weight of homopolymer ofaliphatic diisocyante in the total material formulation can be about26%, e.g., about 27%, about 28%, about 29%, about 30%, about 31%, about32%, about 33%, about 34%, or even about 35%. In some implementations,the percentage weight of homopolymer of aliphatic diisocyante in thetotal material formulation can be from about 20% to about 40%, e.g.,from about 22% to about 38%, from about 24% to about 36%, from about 26%to about 34%, or from about 28% to about 32%.

The isocyanate containing material of the formulation can have aviscosity of at least about 40 Kreb Units (Ku), e.g., at least about 50Ku, at least about 60 Ku, at least about 70 Ku, at least about 85 Ku, atleast about 90 Ku, at least about 91 Ku, at least about 95 Ku, at leastabout 100 Ku, or at least about 105 Ku. In some implementations, theisocyanate containing material of the formulation can have a viscosityof from about 40 Ku to about 140 Ku, e.g., from about 60 Ku to about 105Ku, from about 70 Ku to about 105 Ku, or from about 80 Ku to about 95Ku. In some specific implementations, the isocyanate containing materialof the formulation can have a viscosity of about 85 Ku, e.g., about 87Ku, about 89 Ku, about 91 Ku, about 93 Ku, or about 95 Ku.

Epoxies

An epoxy coating formulation can be obtained by mixing an epoxy resinwith a curing agent. The epoxy resins can include polyether chains thatcontain one or more epoxide units in their structure. Polyethers havethe repeating oxyalkylene units: alkylene substituted by oxygen groups,e.g., ethyleneoxy (—[CH₂—CH₂O]—). In some implementations, the polyetherchains can have additional functional groups such as hydroxyl (—OH).Curing of epoxy resins can lead to less amount of volatile products. Dueto the unique properties of the epoxide ring structure, the curingagents can be either nucleophilic or electrophilic. Examples ofnucleophilic agents include alcohols, phenols, amines, amino silanes,thiols, carboxylic acids, and acid anhydrides. Examples of electrophilicagents include aryl iodonium salts, aryl sulfonium salts, and latentacid catalysts (e.g., dibutyltin diacetate). In some implementations,these curing agents can contain one or more nucleophilic groups. Theepoxy resins themselves can contain an aliphatic (such as cyclic oracyclic) or an aromatic backbone or a combination of both. In someoptional implementations, the epoxy resins can contain othernon-interfering chemical linkages (such as alkyl chains).

For example, the coating 14 described in FIG. 1 can be formed from anepoxy material and an hydroxyl-containing or amine-containing material,at least one of these materials can be in a solvent-based carrier. Insome implementations, the material can be or includes a reaction productof a first component that includes an epoxide or oxirane material (suchas an epoxy prepolymer) and a second component that includes an alcohol,an alkyl amine (such as a cyclic or acyclic alkyl amine), a polyol, apolyamine (such as isophoronediamine), a polyester polyamine, or anamido polyamine. Either or both of the two components can be in asolvent-based carrier. In such implementations, the epoxide or oxiranematerial can serve as a crosslinking material. In some implementations,an oxazolidine can be added to either of the two components to serve asan accelerator to accelerate the reaction between the two components. Insome specific implementations, the epoxide material can beepichlorohydrin, glycidyl ether type (such as diglycidyl ether ofbisphenol-A), oxirane modified fatty acid ester type, or oxiranemodified ester type. In some specific implementations, the polyolmaterial can be a polyester polyol, polyamine polyol, polyamide polyol,or amine adduct polyol. In some implementations, a formulation forpreparing the epoxy coating can be formulated as either a one-componentor a multi-component (e.g., two-component) formulation.

Acrylics

Polyacrylates (also known as acrylics) have the repeating ethylene unitsof the following formula: —[CH₂—CH(X)]—, where X can be —CN, —COOH,alkylOC(O)—, alkylNHC(O)—. An acrylic polymer can be added into asolvent-based carrier (such as those described herein) to form asolution, a dispersion, or an emulsion before forming the coating 14.The acrylic material suitable for preparing coating 14 can includedispersions of acrylic monomers (including functional acrylic monomerssuch as hydroxy acrylates) with a cross-linking catalyst; acryliccopolymers which are capable of self cross-linking; styrene-acryliccopolymers; or functionalized acrylic copolymers.

In some optional implementations, the material used to form the coating14 can be or includes an acrylic material in a solvent-based carrier. Insuch implementations, the acrylic material can be methyl methacrylatebased, butyl acrylate based, ethyl acrylate based, or their mixtures. Insuch implementations, a polycarbodiimide, an aziridine, or animidazoline material can be added to the acrylic material to serve as anexternal cross-linking material. In such implementations, the acryliccoating can be formulated either as a one-component or a multi-component(e.g., two-component) formulation.

Vinylics

In general, vinyl polymers have the repeating unit of the followingformula: —[CX₁X₂—CX₃X₄]—, where X_(i), X₂, X₃ and X₄ can eachindependently be H, halo, alkyl, aryl, or heteroaryl. As an example, thecopolymerization of the vinyl monomers such as polyvinyl chloride withethylene provides varying flexibility and transparency required in manycoatings. In some implementations, the vinylic material can have therepeating unit: —[CH₂—CH(X)]—, where X can be H, halo, alkyl, aryl, orheteroaryl. Polyvinyl chloride has the repeating units of ethylenesubstituted by chlorine: —[CH₂—CH(X)]—, where X is Cl. Polyethylene hasthe repeating units of ethylene: —[CH₂—CH₂]—. In some implementations,the vinylic material suitable for preparing coating 14 can be orincludes a vinyl polymer resin material in a solvent-based carrier. Insuch implementations, the vinylic material can be polyvinyl chloride,polyvinyl chloride-ethylene copolymer, or a thio functionalized vinyliccopolymer.

Alkyds

Alkyd resins are complex polyesters formed by the condensation ofpolyhydric alcohols which contain two or more reactive hydroxyl groups,with polybasic acids which contain two or more reactive carboxylic acidgroups. Examples of polyhydric alcohols include glycerol,pentaerythritol, trimethylolethane, trimethylolpropane, andhexan-1,2,3-triol. Examples of polybasic acids include malonic,succinic, and glutaric acid.

In some implementations, the coating material can be or includes analkyd material in a solvent-based carrier. In such implementations, thealkyd material can be castor oil, soybean oil, sunflower oil, soya oil,linseed oil, tall oil, vinyl toluene alkyd, urethane alkyd, styrenatedalkyd, or their mixtures.

Hybrid Systems

Some or all of the formulation systems mentioned above may be combinedtogether in a solvent-based carrier to form a hybrid system. An hybridsystem typically is an admixture of two types of resins. The hybridsystem can either be a hybrid polymer system in a homogeneous medium ora hybrid polymer system in a non-homogeneous medium (e.g., a hybriddispersion). Hybrid systems can contain two classes of differentpolymers or resins which interact cooperatively to provide desiredproperties, possibly in a solvent-based carrier. In someimplementations, the hybrid material in a solvent-based carrier can bepart of a one-component or a two-component coating material. In suchimplementations, the hybrid material can be a combination ofpolyurethane/acrylic, epoxy/acrylic, alkyd/acrylic, polyvinyl chloride(PVC)/alkyd, PVC/epoxy, or PVC/polyurethane. In such implementations, anexternal cross-linker such as a polycarbodiimide, an aziridine, or animidazoline can be also added to the hybrid system.

Polyols

In general, a polyol used to form the coating 14 can be a compoundcontaining two or more hydroxyl groups, such as an acrylic polyol, apolyoxyalkylene polyol, a polyester polyol, a polyamide polyol, apolyepoxy polyol, a polyvinyl polyol, a polyalkyd polyol, or apolyurethane polyol. A polyol, in general, can be reacted with thereactive groups such as isocyanates, epoxides and other such reactivegroups to produce the coatings.

Acrylic polyols can be typically obtained by polymerization (e.g., by afree-radical mediated polymerization) of hydroxyacrylates, optionally inthe presence of a vinyl monomer (e.g., styrene). Examples ofhydroxyacrylates include butanediol monoacrylate (BDMA), 2-hydroxyethylacrylate (HEA), 2-hydroxypropyl acrylate (HPA), hydroxybutyl acrylate,and polycaprolactone modified hydroxyethyl hexylacrylate. In someimplementations, the percentage weight of an acrylic polyol in the totalcoating formulation can be at least about 12%, e.g., at least about 14%,at least about 15%, at least about 16%, at least about 17%, or even atleast about 18%. In some implementations, the percentage weight of anacrylic polyol in the total material formulation can be from about 10%to about 20%, e.g., from about 11% to about 19%, from about 12% to about18%, from about 13% to about 17%, or from about 14% to about 16%.

A polyoxyalkylene diol is an example of another polyol that can be usedto produce the coatings. In some implementations, the polyoxyalkylenediols can have a number average molecular weight of from about 200 toabout 3,000, e.g., from about 500 to about 2,000, as determined usingnarrow disperse polyethylene glycol standards. Specific examples ofpolyoxyalkylene diols include polyethyleneether glycol,polypropyleneether glycol, polybutyleneether glycol,polytetramethyleneether glycol, and copolymers thereof. Mixtures of anyof the polyoxyalkylene diols can also be used.

Polyesters having terminal hydroxyl groups are another example of apolyol that can be used to produce the coatings. Such polyester diolscan be prepared by the condensation of a diol with a dicarboxylic acidor an equivalent thereof (e.g., an acid halide or an anhydride).Examples of suitable diols include ethylene glycol, 1,2-propanediol,1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol,1,5-pentanediol, 1,3-hexanediol, 1,6-hexanediol, diethylene glycol,dipropylene glycol, triethylene glycol, tetraethylene glycol, ormixtures of these diols. Examples of suitable acids include oxalic,malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic,terephthalic, sebacic, malic, phthalic, cylohexanedicarboxylic ormixtures of these acids. When preparing these polyester diols, generallyan excess of the diol over dicarboxylic acid is used.

A polyurethane diol, having terminal hydroxyl groups is yet anotherexample of a polyol that can be used to produce the coatings. Thepolyurethane diols can include units of polyalkylene, poly(oxyalkylene),polyester, polyamide, polycarbonate, polysulfide, polyacrylate,polymethacrylate, or mixtures of any of these polymers. In someimplementations, the polyurethane diols have a number average molecularweight of from about 200 to 3,000, e.g., from about 500 to about 2,000,as determined using narrow disperse polyethylene glycol standards.Polyurethane diols can be advantageously utilized to provideparticularly wear and scratch resistant coatings. The polyurethanehaving terminal hydroxy groups can be prepared by a reaction of any oneor more of the polyols discussed above and an organic diisocyanate toprovide a isocyanate terminated prepolymer, followed by reaction of theprepolymer with a polyhydric alcohol containing 2-6 hydroxyl groups.Some polyurethane diols are commercially available from Sigma-AldrichChemicals or King Industries.

In some implementations, the isocyanate terminated perpolymer can beobtained by reacting a diol with a diisocyanate utilizing a molar ratioof about 1:2, respectively, in the presence of an activator (oraccelerator) such as oxazolidine or an organotin compound (e.g.,dibutyltin dilaurate or dibutyltin dioctoate). The reaction can beallowed to proceed at a temperature of from about 60° C. to about 180°C. for a period of from about 4 hours to about 24 hours to provide theisocyanate terminated prepolymer.

The isocyanate terminated urethane prepolymer can then be reacted, e.g.,from about 60° C. to about 110° C. for about 1 hour to about 10 hours,with a monomeric, polyhydric alcohol containing 2-6 hydroxyl groups in amolar ratio of 1:2, respectively. Examples of monomeric, polyhydricalcohols that can be used include 1,4-cyclohexane dimethanol,1,4-butanediol, mannitol, trimethylol propane, trimethylol ethane,1,1-cyclohexane dimethanol, hydrogenated bisphenol A, cyclohexane diol,neopentyl glycol, trimethylpentanediol, pentaerythritol, andtrimethylhexanediol. The result of treating the isocyanate terminatedurethane prepolymer with the one or more alcohols is a polyurethane diolhaving 2-10 terminal hydroxy groups and no isocyanates groups.

Polyurethane diols can also be made by reacting organic carbonates withamines.

In some implementations in which a polyurethane diol and analkoxyalkylamino material are used to make the coating, the molar ratioof polyurethane diol to the alkoxyalkylamino material can range fromabout 10:1 to about 1:1, e.g., from about 5:1 to about 1:1.

Examples of commercial polyols include, but are not limited to,Desmophen® (available from Bayer), Macrynal® (available from CytecIndustries) and Arolon® (available from Reichold).

In some optional implementations, the coating material can be orincludes a reaction product of a first component that includes analkoxyalkylamino material in a solvent-based carrier and a secondcomponent that includes a polyol in a solvent-based carrier. In suchimplementations, the alkoxyalkylamino material can serve as across-linking material.

In yet other optional implementations, the coating materials can includerosin phenolic resin, epoxy ester resin, fluorine based resins (such asfluorine modified acrylic, fluorine modified epoxy, fluorine modifiedalkyd, or fluorine modified polyurethane), siloxane based resins (suchas hydroxy-functional polydimethylsiloxane e.g., hydroxyalkylpolydimethylsiloxane), silica based resins (such as silica modifiedacrylic, silica modified epoxy, silica modified alkyd, or silicamodified polyurethane).

Solvents

The coating 14 can be formed from a material in a solvent-based carrier,e.g., an organic solvent. While not intending to be bound by theory, itis believed that solvents can be effective as a dispersive vehicle forthe pigments and resins in a coating formulation prior to curing. Duringthe application of the formulation, they aid in achieving an appropriateviscosity of the formulation. However, after the coating has been cured,it can be expected that there is no residual solvent. The solvents caninclude 2-butoxyethanol, ethylene glycol, ethyl benzene, xylenes, methylamyl ketone, isopropyl alcohol, propylene glycol monomethyl ether,ethylene glycol monobutyl ether, butanol, paraffins, alkanes,polypropylene glycol, Stoddard solvent, toluene, ethoxylatedalkylphenol, 1-methyl-2-pyrrolidinone, or 1-ethylpyrrolidin-2-one. Insome implementations, the solvent can be or includes hydrocarbons (suchas saturated hydrocarbons and unsaturated hydrocarbons), alcohols (suchas alkoxy alcohols, ketonic alcohols), ketones, esters (such asacetates), glycol ethers, and glycol ether esters. Examples ofhydrocarbons include toluene, xylene, naphtha (petroleum), petroleumdistillates, ethyl benzene, trimethyl benzenes, and fractions ofhydrocarbon mixtures obtained from petroleum refineries. Mixtures of anytwo or more of these solvents may also be utilized. Examples of alcoholsinclude ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol,benzyl alcohol, 2-(n-propoxy)ethanol, 2-(n-butoxy)ethanol,3-(n-propoxy)ethanol, and 2-phenoxyethanol. Mixtures of any two or moreof these solvents may also be utilized.

Examples of ketones include acetone, methyl ethyl ketone, methyln-propyl ketone, methyl n-butyl ketone, and methyl isoamyl ketone.Mixtures of any two or more of these solvents may also be utilized.

Examples of esters include ethyl propanoate, ethyl butanoate, ethylglycolate, propyl glycolate, butyl glycolate, and isoamyl glycolate,methyl acetate, ethyl acetate, n-butyl acetate, isoamyl acetate, andt-butyl acetate. Mixtures of any two or more of these solvents may alsobe utilized.

Other Modifying Agents in the Formulations

Accelerators are agents that speed up the curing process. Acceleratorsthat can be used in the formulation include dibutyltin dialkanoate(e.g., dibutyltin dialaurate, dibutyltin dioctoate), and oxazolidine.Acid promoters are also agents that speed up the curing process. Acidpromoters include aryl, alkyl, and aralkyl sulfonic acids; aryl, alkyl,and aralkyl phosphoric and phosphonic acids; aryl, alkyl, and aralkylacid pyrophosphates; carboxylic acids; sulfonimides; mineral acids andmixtures thereof. Examples of sulfonic acids include benzenesulfonicacid, para-toluenesulfonic acid, dodecylbenzenesulfonic acid, andnaphthalenesulfonic acid. Examples of aryl, alkyl, and aralkylphosphates and pyrophosphates include phenyl, para-tolyl, methyl ethyl,benzyl, diphenyl, di-para-tolyl, di-methyl, di-ethyl, di-benzyl,phenyl-para-tolyl, methyl-ethyl, phenyl-benzyl phosphates andpyrophosphates. Examples of carboxylic acids include citric acid,benzoic acid, formic acid, acetic acid, propionic acid, butyric acid,dicarboxylic acids such as oxalic acid, and fluorinated acids such astrifluoroacetic acid. Examples of sulfonimides include dibenzenesulfonimide, di-para-toluene sulfonimide, methyl-para-toluenesulfonimide, and dimethyl sulfonamide. Examples of mineral acids includephosphoric acid, nitric acid, sulfuric acid and hydrochloric acid. Insome implementations, phosphoric acid, citric acid or a combinationthereof can be utilized as an acid promoter.

Surface additives can modify the surface characteristics (such assurface tension properties, substrate wetting, gloss, feel, and slip) ofthe writable-erasable surface 16. Examples of surface additives caninclude modified polydimethyl siloxanes and polytetrafluoroethylene. Thecurable compositions can also contain other optional ingredients such asfillers, surfactants, light stabilizers, pigments, opacifying agents,defoaming agent, surface gloss-modifying agent, biocides,viscosity-modifying agent, dispersing agents, reactive diluents,extender pigments, inhibitors for corrosion or efflorescence, flameretardants, intumescent agents, thermal agents for energy efficiency,additives for protection from UV and/or IR, self-cleaning agents,perfumes, or odor sustaining agents.

Several commercial suitable light stabilizers are available from CIBASpecialty Chemicals under the trade names TINUVIN® (benzotriazole,triazine, or hindered amine based) and CHIMASSORB® (benzophenone based).

Wetting agents can modify the viscosity characteristics of the coatingformulations. Examples of wetting agents can include silicone freefamily of agents, Metolat® available from Munzing Chemie GmbH.

Examples of opacifying agents can include zinc oxide, titanium dioxide,silicon dioxide, Kaolin clay, e.g., high whiteness Kaolin clay, ormixtures thereof.

Defoaming agents can release the trapped air in the coatings and canenhance the surface smoothness. Examples of defoaming agents can includepolyethylene glycols, or silicone surfactants, e.g., polyether modifiedpolydimethyl siloxane. Defoaming agents such as the BYK family of agentsare available from BYK-Chemie GmbH.

Examples of viscosity modifying agents include polyurethanes, or acommercial acrylic copolymer, TAFIGEL®, available from Munzing ChemieGmbH.

Certain implementations are further described in the following examples,which are not intended to limit the scope of the disclosure.

EXAMPLES Example 1

First Component: During the grind stage, to the pot were added, in orderand in the ranges of weight % listed in Table 1: ethyl benzene, n-butylacetate, xylene, acrylic polyol, Stoddard solvent, butylglycolate,2-butoxyethanol, and methyl iso-amyl ketone. The contents were thenmixed at slow speeds until fully dispersed. The speed was maintained atno more than 100-200 rpm. Titanium dioxide, aluminum hydroxide,amorphous silica and water were added to the mixture in the pot, whileincreasing the speed to achieve a good vortex. Final RPM settings werebetween 2,000-3,000 rpm. The speed was adjusted until maximum shear wasobtained with minimal integration of air and mixed for 10-15 minutes, ora Hegman of 5-6. After ascertaining that there were no chunks,crystalline silica was added while increasing speed to achievesufficient vortex. A sufficient RPM was maintained to get thetemperature in the pot up to 95-110° F. within 10-15 minutes. The grindspeed was maintained for additional five minutes then decreased by25-35% to allow the heat to dissipate. Hegman at this point was at leasta 7. Once Hegman was achieved, mixing speed was reduced until the potwas just mixing the raw materials and continued for 30 minutes.

During the letdown stage, ethyl benzene, n-butyl acetate, xylene, andacrylic polyol were added to the grind mixture. After less than 5-10minutes, dibutyltin dilaurate, methyl iso-amyl ketone, and n-butylacetete were added to the pot. The speed was maintained to mix thematerial. After 5-10 minutes, xylene and 2-phenoxyethanol were addedwhile maintaining speed to mix in material. After 5-10 minutes propionicacid was added while maintaining mixing speed. After 5-10 minutes amixture of crystal violet, methyl iso-amyl ketone, and n-butyl acetatewas added while mixing and maintaining speed (crystal violet has atendency to adhere to the shaft or sidewalls of the pot; scrapping thewalls helped color uniformity). After 30 minutes the product waspackaged.

Second Component: The homopolymer hexamethylene diisocyanate andhexamethylene-1,6-diisocyanate mixture was the second part of the finalproduct. No mixing was required for these materials.

Combining the First and Second Components: The first and secondcomponents were combined, when desired, to obtain the final coatingformulation. The combination had a pot life of a maximum of about 1 hourduring which time the application was completed. The composition of theformulation is described in the Table 1 under Example 1. The typicalproperties of the coating are presented in Table 2.

Example 2

The procedure described in Example 1 was followed with attention to thefact that times for grinding were different. However, the total timeneeded for grind stage was not more than 2 hours. Additionally, thetimes for letdown were different. The total mixing time for letdownstage procedure was not more than 2-3 hours. The weight percentageranges of the components in the final composition mixture are shownunder Example 2 of Table 1.

Example 3

The procedure described in Example 1 can be followed with attention tothe fact that times for grinding will vary. However, the total timeneeded for grind stage should not be more than 2 hours. Additionally,the times for letdown will vary. The total mixing time for letdown stageprocedure should not be more than 2-3 hours. The weight percentageranges of the components in the final composition mixture are shownunder Example 3 of Table 1.

TABLE 1 Composition described in Examples 1-3 Weight percent in totalformula Component Example 1 Example 2 Example 3 Homopolymer of 32 23-2828-34 Hexamethylene diisocyanate Titanium dioxide 17 17-21 16-18 n-Butylacetate 16 11-15 14-18 Acrylic polyol 13 13-15 12-14 Xylenes 7 1-5 6-8Methyl isoamyl ketone 3 0.01-0.03 1-5 Water 3 6-8 2-4 Silica, amorphous2 1-3 1-3 Aluminum hydroxide 2 1-3 1-3 Ethyl benzene 2 0.47-0.53 1-3Stoddard solvent 1 0.5-2   0.5-2   Hexamethylene diisocyanate 0.190.14-0.17 0.21-0.22 Ethylene glycol monophenyl 0.09 — — ether Butylglycolate 0.04 0.02-0.06 0.02-0.06 Dibutyltin dilaurate 0.01 0.02-0.050.005-0.02  2-Butoxyethanol 0.01 0.005-0.02  0.005-0.02  Silica,crystalline 0.01 0.005-0.02  0.005-0.02  C.I. Basic violet 1 0.0003 —0.0004-0.0005

TABLE 2 Typical properties of the coating formulation Test DescriptionExample 1 Porosity, % 30 Surface roughness, R_(a) (nm) 2612 Swardhardness, # of rocks 23 Gloss 20 Degree 47.1 60 Degree 84.7 85 Degree86.8 Contact angle, degrees (with D.I. water) 65.00 Surface tension,dynes/cm 30

Example 4

The components described in the Table 3 below can be mixed, following aprocedure similar to that described in Example 1, to obtain an epoxybased formulation containing the components having the weight percentageranges indicated in the table. This formulation could be used either asa one-component system or as part of a two-component system.

TABLE 3 range % by wt on Description total formula Oxirane-modifiedfatty acid ester 17-20 Stoddard solvent 0.10-0.14 Butylglycolate0.005-0.02  2-Butoxyethanol 0.001-0.006 Alkylarylalkoxylate 0.02-0.13Ester/styrene maleic anhydride 0.01-0.10 copolymer Ethylene glycol0.01-0.03 2,4,7,9-Tetramethyl-5-decyne-4,7-diol 0.01-0.03 Ethyl benzene0.04-0.07 Xylene, mixed isomers, pure 0.4-0.6 Titanium dioxide 13-15Aluminum hydroxide 1-3 Amorphous silica 1-3 Water 4-6 Propylene glycolmonomethyl ether 1-3 Methyl amyl ketone 5-7 Isopropyl alcohol 3-6 Highacid value polyester 20-23 Ethylene glycol monobutyl ether 4-6 Isopropylalcohol 4-6

Example 5

The components described in the Table 4 below can be mixed, following aprocedure similar to that described in Example 1, to obtain an alkydbased formulation containing the components having the weight percentageranges indicated in the table. This formulation could be used either asa one-component system or as part of a two-component system.

TABLE 4 Range % by Description wt on total formula Ethyl benzene0.19-0.40 Xylene 0.85-2.8  Alkyd resin 39-45 Stoddard solvent  7-25Crystalline silica 0.20-0.40 Iso-butanol 0.15-0.25 Titanium dioxide25-34 Aluminum hydroxide 0.01-3   Amorphous silica 0.01-5   Water  6-16Methyl ethyl ketoxime 0.60-0.80 Cobalt neodecanoate 0.05-2   Neo c9-13acid, cobalt salts 0.05-2   Diethylene glycol methyl ether 0.005-2   Neodymium 2-ethylhexanoate 1-4 Diethylene glycol butyl ether 0.10-0.302,2-bipyridyl 0.08-1.5  PG monomethyl ether 0.10-0.30 DPG monomethylether 0.005-2    Aluminum salt 2.2-2.5

Example 6

The components described in the Table 5 below can be mixed, following aprocedure similar to that described in Example 1, to obtain an acrylicbased formulation containing the components having the weight percentageranges indicated in the table.

TABLE 5 Range % by Description wt on total formula Acrylic polymer(s)26-30 Methyl amyl ketone 8.5-9.5 Stoddard solvent 0.30-0.70Butylglycolate 0.04-0.07 2-butoxyethanol 0.01-0.02 Methyl amyl ketone1-4 N-butyl acetate 1-4 Titanium dioxide 21-27 Aluminum hydroxide0.01-10   Amorphous silica 0.01-3   Water  6-10 Dibutyltin dilaurate0.01-0.04 Methyl amyl ketone 0.05-2   N-butyl acetate 0.05-2   Xylene0.20-0.50 2-phenoxyethanol 0.09-0.12 Homopolymer hexamethylene 46-77diisocyanate N-butyl acetate  7-16 Xylene  4-11 Ethyl benzene 0.05-2.5 Hexamethylen-1,6 diisocyanate 0.03-0.50

Example 7

The components described in the Table 6 below can be mixed, following aprocedure similar to that described in Example 1, to obtain an acrylicbased formulation containing the components having the weight percentageranges indicated in the table.

TABLE 6 Range % by Description wt on total formula Vinylic acrylicpolymer(s) 26-30 Methyl amyl ketone 8.5-9.5 Stoddard solvent 0.30-0.70Butylglycolate 0.04-0.07 2-butoxyethanol 0.01-0.02 Methyl amyl ketone1-4 N-butyl acetate 1-4 Titanium dioxide 21-27 Aluminum hydroxide0.01-10   Amorphous silica 0.01-3   Water  6-10 Dibutyltin dilaurate0.01-0.04 Methyl amyl ketone 0.05-2   N-butyl acetate 0.05-2   Xylene0.20-0.50 2-phenoxyethanol 0.09-0.12 Homopolymer hexamethylene 46-77diisocyanate N-butyl acetate  7-16 Xylene  4-11 Ethyl benzene 0.05-2.5 Hexamethylen-1,6 diisocyanate 0.03-0.50

Example 8 Quantitative Determination of the Erasable Characteristics ofthe Writable-Erasable Surface

The color stimulus, which is the radiation from the colored object thatproduces the perception of that color, was measured. Color perception isaffected not only by the spectral make up of the object, but also thelight source under which it is viewed. If the spectral distribution ofthe light source and the relative spectral reflectance of the object areknown, then the spectral composition reaching the eye of an observerwith normal vision from the object illuminated by that source can becalculated. The Commission Internationale de L'Eclairage (CIE) has setup procedures for calculation of the color differences in a CIELAB colorspace.

The formulation in Example 1 was coated over a piece of dry wall. Themarkings were made using red, blue and green Expo 1 markers followed byerasing with the Quartet Ghost Duster® eraser. The X-Rite Sp-62Spectrophotometer was used to take the color readings and to calculateL*, a*, and b* values automatically. The values were then recorded. Thechanges were calculated according to ASTM Test Method D2244, asdifferences in the L*, a*, and b* values, where the direction of thecolor difference is described by the magnitude and the algebraic signsof the components, ΔL*, Δa*, Δb*. The values were then calculated asfollows:ΔL*=L* ₁ −L* ₀  (1)Δa*=a* ₁ −a* ₀  (2)Δb*=b* ₁ −b* ₀  (3)where L*₀, a*₀, b*₀ refers to the reference, and L*₁, a*₁, b*_(i),refers to the test specimen. Table 7 shows the magnitude and directionof each color value and what color change occurs.

Table 7. Meanings of Color Values

TABLE 7 Meanings of Color Values Direction Color Change Value Result +L* Lighter − L* Darker + A* Redder (less green) − A* Green (less red) +B* Yellow (less blue) − B* Bluer (less yellow)By choosing one sample to be the reference point, the change in colorfrom this reference point is called the color difference (ΔE), which iscalculated from the equation:ΔE=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2)  (4)The measured color difference (ΔE) after certain number of cycles ofwriting and erasing, for the writable-erasable surface of the curedcoating obtained from the formulation described in Example 1, aretabulated in Table 8.

TABLE 8 Cycle ΔL* Δa* Δb* ΔE 0 93.38 −0.90 −0.01 0.0 500 93.15 −0.93−0.03 0.23 1000 92.61 −1.13 0.79 1.14 1500 92.03 −1.35 1.27 1.92 200090.81 −1.61 1.72 3.17 2500 91.16 −1.67 1.75 2.94 3000 90.94 −1.77 1.593.04 3500 91.63 −1.69 1.45 2.41 4000 90.09 −2.37 1.84 4.05 4500 90.97−1.92 1.63 3.08 5000 89.74 −2.22 2.12 4.42 5500 90.37 −2.19 1.96 3.826000 90.45 −2.24 1.92 3.76 6500 88.84 −2.31 2.46 5.36 7000 88.78 −1.832.65 5.40 7500 89.84 −2.19 2.48 4.52 8000 89.25 −2.06 2.69 5.07 850089.28 −2.14 2.55 4.99 9000 90.14 −2.44 2.09 4.16 9500 88.44 −2.17 3.015.92 10000 89.55 −2.06 2.86 4.92

Example 9 Determination of Erasable Characteristics of aWritable-Erasable Surface

The nature of visual change (erasable characteristics) on thewritable-erasable surface can be evaluated by the visual changeperceived after the surface has been marked followed by erasing themarking. It can be characterized by the leave behind which can bedetermined after 1 or 2 passes by the eraser to erase the marking: themarkings may seem to stick to the surface and they might erase as instreaks or might be spotty. The quality of the surface can also bemeasured by the dirtiness which can be determined after one pass withthe eraser over the marked area, a faint to dark cloud might be leftfrom the eraser, like smearing of the marking due to the eraser. Both“leave behind” and “dirtiness” can be measured on a scale of zero to tenbased on the degree to which the marking material can be removed fromthe surface. The lower number indicates a better surface performance.

Example 10 ΔL*—Value Determination

An aluminum sheet was primed with one coat of Kilz Premium primer(available from Masterchem Industries) followed by application of onecoat of the coating formulation (obtained by mixing the first and secondcomponents described in Example 1) applied with a 8 mil box drawdown.The coated sheet was then allowed to cure for 12 days. The sheets withthe cured coating were mounted on a Taber abrader 4360 instrument(available from Taber Industries), and the writable-erasable surface isabraded with CS-10 abrasion wheels (a medium softness wheel type) using250 gram weights on the balancing arm. The wheels were cleaned every 500cycles using a sand cleaning paper (supplied by Taber Industries). Therelative humidity was 60%, the ambient temperature was 70° F. at thetime of testing. The writable-erasable surface was sampled after 0, 100,200, 500 and 1000 cycles. The L-value (L*) was measured with the X-RiteSp-62 Spectrophotometer at each sample point (0, 100, 200, 500 and 1000cycles) and Expo 1 and Expo 2 blue and black markers were applied to theabraded area. The marking was erased with an Expo felt dry eraser andthen the L-value (L*) was again measured. The change in lightness, ΔL*value (See Table 9), from these two measurements represents the amountof marker remaining over the abraded area that could not be removed.

TABLE 9 ΔL* Expo 1 Expo 2 Average No. of cycles Black Blue Black BlueΔL* 0 94.56 94.56 94.56 94.56 94.56 50 90.04 89.99 83.48 90.86 88.59 10088.34 88.53 79.87 88.52 86.32 150 84.81 88.56 76.96 88.96 84.82 20081.56 86.61 77.90 86.14 83.05 500 85.94 89.40 67.17 78.68 80.30 100086.56 89.62 71.58 89.23 84.25

Example 11 Application of the Coating

The application is performed in a clean, dustless environment. Prior toinstallation, the ambient temperature within the application site ismaintained at not less than 45° F. for a minimum of 24 hours and properventilation of application areas is ascertained to minimize odors invicinity of application. The surface of the substrate to be painted onis primed, using a non-tinted PVA or vinyl acrylic interior latexprimer, until the color of the existing surface does not show through.The primer is allowed to dry completely according to manufacturer'srecommendation. The surface is painted in approximately 2 foot widesections by working from one end to the other. Each section is completedbefore painting the next section. A wet edge is maintained to avoid lapmarks. A single coat is applied using foam roller covers. The equipmentis cleaned with acetone or denatured alcohol. The coating is typicallyallowed to cure for 1 week, at room temperature, to form thewritable-erasable surface.

The writable-erasable surface can be maintained by daily erasure andcleaning with a standard dry-erase eraser or a dry cloth. For periodicand more thorough cleaning, a damp cloth may be used.

If it is desired to strip off the writable-erasable surface or recoatany damaged surface, the original surface is deglossed by sanding thesurface and priming before application of the dry erase coating.

OTHER IMPLEMENTATIONS

A number of implementations have been described. Nevertheless, it willbe understood that various modifications can be made without departingfrom the spirit and scope of the disclosure. Accordingly, otherimplementations are within the scope of the following claims.

For example, while rollers have been described for applying thematerials, brushes, pre-loaded applicators, or sprayers can be used.When sprayers are used, the precursor materials can be first mixed andthen sprayed onto a substrate, or the precursors materials can each besprayed from separate nozzle outlet, the mixing of the precursorsoccurring in flight toward the substrate and/or on the substrate.

While whiteboards and coated walls have been described, the coatings canbe applied to other forms. For example, referring now to FIG. 3, any ofthe materials described herein can be applied to a continuous sheet ofmaterial, such as paper, to provide a product 50 that includes asubstrate 52 and a coating 54 extending upon the substrate 52. As shownin FIG. 3, the product 50 can be conveniently stored in a roll form. Ifdesired, product 50 can be cut, e.g., along a transverse line 60, toprovide individual sheets 70 of material. Referring now to FIG. 4,sheets 70 can be fashioned into a product 80 in tablet form usingfasteners 82. If desired, the assembled sheets can have perforations 86,allowing sheets to be torn from the tablet and used as a mobilewritable-erasable product.

Blends of polyurethane materials and any one of, some of, or all ofepoxy resins, acrylic resins described herein can be used to make thecoatings having the writable-erasable surface.

Other solvent-based materials may be used alone, or in combination withother solvent-based materials described herein, such as polyurethanematerials. For example, epoxy resins in a solvent-based carrier may beutilized. These epoxy resins may be used in conjunction with variouscross-linkers and/or additives described herein. For example, thecross-linkers can be a moiety that includes a plurality of amino groups,thiol groups, hydroxyl groups or mixtures of such groups. Water-basedepoxy resins are commercially available under the name Enducryl® fromEpoxy Systems, Inc.

The first and second components can be applied to the substrate, e.g.,by concurrently spraying the components so that they mix in flightand/or on the substrate, and then optionally applying a cross-linkingpromoter, such as an acid, to the mixed first and second components,e.g., in the form of a solution. In still other implementations, across-linking promoter is first applied to the substrate, and then thefirst and second components are applied to the substrate having thecross-linking promoter.

The first and second components can be mixed, e.g., by alternatelyadding the desired, pre-determined quantities of the components from alarge drum to a paint bucket, mixing, and then applying the coating on asubstrate. The advantage of this method is that the pot life of thecomponents are preserved without wasting the components.

Still other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A method of forming a coating having awrite-erasable surface on a substrate comprising: combining anisocyanate resin component and an acrylic polyol resin component inrelative amounts with respect to each other to produce a composition,wherein the composition is in an organic solvent-based carrier, andfurther wherein a) the isocyanate resin component comprises 20-40% byweight of the composition, and b) the acrylic polyol resin componentcomprises 10-20% by weight of the composition; applying the compositionto a substrate, to cure under ambient conditions so that a coatinghaving a write-erasable surface is produced on the substrate, thecoating being characterized by: a gloss finish greater than 65 whenmeasured at 60°; an average surface roughness of less than 7,500 nm anda maximum surface roughness of less than 10,000 nm; a Sward hardness ofgreater than about 10; a Taber abrasion of less than 150 mg/thousandcycles; an elongation at break is between about 5 percent and about 400percent; a sag resistance is between about 4 mils to about 24 mils; anda contact angle measured using deionized water of less than about 150degree, and so that after the coating is marked with a marking materialcomprising a colorant and a solvent, the marking material can be erasedfrom the write-erasable surface to be effectively invisible.
 2. Themethod of claim 1, wherein the step of combining comprises: obtaining afirst material comprising the isocyanate resin component; obtaining asecond material, physically separate from the first material, thatcomprises the acrylic polyol resin component; and combining the firstand second materials with one another.
 3. The method of claim 2, whereinthe first and second materials are maintained physically separate fromone another in first and second containers.
 4. The method of claim 1,wherein the second material further comprises a cross-linking agent. 5.The method of claim 1, wherein the isocyanate resin component isselected from the group consisting of hexamethylene diisocyanate (HDI),tetramethylene diisocyanate, octamethylene diisocyanate, decamethylenediisocyanate, 2-methylpentane-1,5-diisocyanate, toluene diisocyanate(TDI), diphenylmethane diisocyanate (MDI), m- and p-phenylenediisocyanates, bitolylene diisocyanate, cyclohexane diisocyanate (CHDI),bis-(isocyanatomethyl) cyclohexane (H6XDI), dicyclohexylmethanediisocyanate (H12MDI), dimer acid diisocyanate (DDI), trimethylhexamethylene diisocyanate, lysine diisocyanate and its methyl ester,methyl cyclohexane diisocyanate, 1,5-napthalene diisocyanate, xylenediisocyanate, polyphenylene diisocyanates, isophorone diisocyanate(IPDI), hydrogenated methylene diphenyl isocyanate (HMDI), tetramethylxylene diisocyanate (TMXDI), oligomers and homopolymers of any of theforegoing, and mixtures thereof.
 6. The method of claim 1, wherein theisocyanate resin component is selected from the group consisting of analiphatic diisocyanate, its oligomer, its homopolymer, and mixturesthereof.
 7. The method of claim 1, wherein the isocyanate resincomponent is a hexamethylene-1,6-diisocyanate homopolymer.
 8. The methodof claim 1, wherein the solvent-based carrier is selected from the groupconsisting of hydrocarbons, alcohols, ketones, esters, mineral spirits,bio-based solvents, and mixtures thereof.
 9. The method of claim 1,wherein the solvent-based carrier is selected from the group consistingof ethyl benzene, xylene, n-butyl acetate, methyl iso-amyl ketone,Stoddard solvent, t-butyl acetate, acetone, isopropyl alcohol,2-butoxyethanol, toluene, methanol, propanol, 2-butanol, iso-amylalcohol, methyl amyl alcohol, pentane, heptane, odorless mineralspirits, methyl ethyl ketone, diacetone alcohol, methyl amyl ketone,ethyl amyl ketone, diisobutyl ketone, methyl heptyl ketone, ethylacetate, isopropyl acetate, propyl acetate, isobutyl acetate, n-butylacetate, glycol ether EM acetate, amyl acetate, isobutyl isobutyrate,glycol ether EE acetate, Glycol ether EB acetate, 2-ethylhexyl acetate,glycol ether DE acetate, Glycol DB acetate, methyl isobutyl ketone,dipropylene glycol butoxy ether, vegetable oil, corn oil, sunflower oil,and mixtures thereof.
 10. The method of claim 1, wherein the step ofcombining further comprises combining an accelerator with the isocyanateresin component and the acrylic polyol resin component.
 11. The methodof claim 10, wherein the accelerator comprises dibutyltin dilaurate. 12.The method of claim 1, wherein the step of combining further comprisescombining an acid promoter with the isocyanate resin component and theacrylic polyol resin component.
 13. The method of claim 12, wherein theacid promoter comprises propionic acid.
 14. The method of claim 1,wherein the step of combining further comprises combining titaniumdioxide, a surface additive, a wetting agent, or a defoaming agent withthe isocyanate resin component and the acrylic polyol resin component.15. The method of claim 1, wherein the step of combining furthercomprises combining a pigment or a colorant with the isocyanate resincomponent and the acrylic polyol resin component.
 16. The method ofclaim 1, wherein the coating is characterized in that, the markingmaterial can be erased from the write-erasable surface to besubstantially invisible after writing and erasing at the same positionfor more than about 100 cycles.
 17. The method of claim 1, wherein thecoating is characterized in that, the marking material can be erasedfrom the write-erasable surface to be substantially invisible afterwriting and erasing at the same position for more than about 5,000cycles.
 18. The method of claim 1, wherein the substrate is selectedfrom the group consisting of cellulosic material, glass, wall, fiberboard, particle board, gypsum board, wood, plastic, densified ceramics,stone, and metal.
 19. The method of claim 1, wherein the substratecomprises a flexible film or a rigid structure.
 20. The method of claim1, wherein the step of applying comprises rolling, painting, spraying orany combination thereof.
 21. The method of claim 1, further comprising astep of permitting the composition to cure.
 22. The method of claim 1,further comprising a step of writing with the marking material on thewrite-erasable surface.
 23. The method of claim 22, further comprising astep of erasing the marking material.
 24. The method of claim 1, whereinthe step of applying comprises forming a coating having a thickness ofat least 20 mil.